In　order　to　treat　domestic　wastewater　with　high　ammonia　but　low　carbon　source　(low　C/N　ratio),　a　novel　two　sludge　pre-A(2)NSBR　system　(anaerobic/anoxic/aerobic　nitrification)　was　firstly　developed　by　exchanging　the　sequence　of　aerobic　nitrification　and　anoxic　phase　of　the　conventional　A(2)NSBR　process　(anaerobic/　aerobic　nitrification/anoxic).　The　system　was　operated　for　186　days　to　treat　real　domestic　wastewater　with　low　carbon/nitrogen　(C/N　=　4.03).　Anoxic　duration　was　adjusted　and　post-aeration　phase　was　added　to　enhance　nitrogen　and　phosphorus　removal.　Results　indicate　that　adding　post-aeration　phase　is　indispensable　to　achieve　enhanced　phosphorus　removal,　the　pre-A(2)NSBR　system　achieved　a　high　denitrifying　phosphorus　removal　efficiency　of　96.86%　with　efficient　utilization　of　limited　carbon　source.　Specifically,　the　ammonia　effluent　was　0.46　mg/L,　which　solved　the　bottleneck　problem　of　high　ammonia　residues　in　conventional　A(2)NSBR　process.　The　fluorescence　in　situ　hybridization　(FISH)　results　showed　that　PAOs　was　enriched　and　GAOs　was　inhibited　in　the　A(2)SBR,　nitrifiers　also　became　dominant　in　the　N-SBR.　Moreover,　the　profiles　variation　of　real-time　online　indicator　such　as　pH,　ORP　and　DO　were　demonstrated　closely　related　with　the　nutrient　removal　performance,　and　based　on　this,　it　is　possible　or　expected　to　establish　the　real　time　control　strategy　in　the　future.　(C)　2016　Elsevier　B.V.　All　rights　reserved.